Hollow thermoplastic containers have long been produced by the blowing of an extruded tube captured between two mold halves. The captured extruded tube will have a portion which extends out of the blow mold adjacent to the neck portion of the mold. When the blow pin tip is lowered into the extruded tube, to a point adjacent or below the neck portion of the mold, the outside portion of the extruded tube, generally referred to as the neck moil, is pinched between a cutter collar mounted above the blow pin tip and an anvil formed by the blow mold halves. The introduction of the blow pin tip also forge forms the neck finish and provides a conduit for the introduction of blow air to the interior of the captured extruded tube. Blow air is then introduced through the blow pin tip to inflate the captured tube to the shape of the mold halves. Cooling fluid is passed through internal traces in the mold halves thereby cooling the blown container to insure that it is rigid enough to remove from the mold. The neck moil must then be removed from the completed container so that a commercially acceptable product is produced. Despite the pinching action of the cutter collar the neck moil generally will still adhere to the container neck principally due to the fact that the neck moil is not cooled and remains fairly soft and plastic. Removal is conventionally achieved by engaging a rotation collar, which fits about the cutter collar, with the moil so that the moil can be tightly gripped and rotated to shear it from the container. Such a procedure is mechanically efficient and is ideally suited when producing containers having conventional neck finishes, i.e. neck finishes with forge formed structure, such as a helical thread, about the outside surface of the neck finish but without any forge formed structure about the inside surface of the neck finish. However, when it is necessary to produce the neck finish having molded structure about its inside surface, the utilization of the rotative movement to aid in neck moil removal cannot be used. This is due to the fact that the blow pin tip carries die to form the inside surface molded structure and thus rotation of the blow pin tip will result in damage or disfigurement of the molded structure as such structure will be in rotative interference with the die that produced it.
Therefore, it is an object of this invention to provide a blow pin assembly which utilizes rotative motion, in combination with a cutter collar and a rotation collar, to remove the neck moil from a blow molded article which at the same time is capable of forming a neck finish for the blown article, which neck finish has molded structure about its outside surface and about its inside surface.